This invention provides a process for preparing surfactant compositions comprising secondary alkyl sulfates which are substantially free of unreacted organic matter (UOM) and which are substantially free of water, thus making the compositions substantially free of inert diluents.
In conventional practice, secondary alkyl sulfates have been prepared by reaction of an olefin with sulfuric acid followed by neutralization of the intermediate secondary alkyl sulfuric acid with aqueous base, usually sodium hydroxide. The process is complicated by incomplete reaction of the starting olefin and by formation of dialkyl sulfates which saponify during the neutralization step, noted above, to equal molar amounts of secondary alkyl sulfate and secondary alcohol. These reactions, i.e., sulfation, neutralization and saponification, may be illustrated by the following equations: EQU R.sup.= +H.sub.2 SO.sub.4 .fwdarw.ROSO.sub.3 H+R.sub.2 SO.sub.4 EQU ROSO.sub.3 H +NaOH .fwdarw.ROSO.sub.3 Na+H.sub.2 O EQU R.sub.2 SO.sub.4 +NaOH.fwdarw.ROSO.sub.3 Na+ROH
Unreacted olefin and secondary alcohol which can amount to 50% by weight or more of the starting olefin, are generally removed from the secondary alkyl sulfate by a process of extraction with an organic solvent as described in U.S. Pat. No. 4,175,092. The extraction process can be complicated by the formation of undesirable emulsions and gels as well as by the dissolution of some of the extracting solvent in the aqueous secondary alkyl sulfate phase. Extracting solvents frequently have objectionable odors and must be removed from the aqueous surfactant solution, an operation which can be accompanied by severe foaming difficulties. When extraction is complete the concentration of secondary alkyl sulfate in water is generally in the range of 20-40% by weight (F. Asinger, Mono-Olefins: Chemistry and Technology, 1968 pp. 689-694).
It would therefore be advantageous to have a process for preparing surfactant compositions utilizing secondary alkyl sulfates as the anionic component which eliminates the problems associated with solvent extraction for removal of the non-surface active organic material and which produces a product free of water, thus allowing maximum handling and blending flexibility.
An integrated process for preparing surfactant compositions has been found in which secondary alkyl sulfates derived from olefins can be generated in a manner such that the non-surface active material can be easily stripped from the secondary alkyl sulfates while at the same time producing a surfactant and/or detergent composition which is particularly useful for household laundry applications.
It is therefore an object of this invention to prepare surface active compositions containing olefin-drived secondary alkyl sulfates, which are substantially free of unreacted olefin and substantially free of water, in a nonionic surfactant having a boiling point higher than the olefin and its corresponding secondary alcohol. In the present invention, a surface active composition is prepared by reacting a detergent range olefin with concentrated sulfuric acid, removing excess sulfuric acid, neutralizing and saponifying the mixture in the presence of a base dispersed in a nonionic surfactant having a boiling point higher than the detergent range olefin and its corresponding secondary alcohol, and then passing the mixture through a falling film or wiped film evaporator to strip unreacted organic matter from the mixture, thereby producing a secondary alkyl sulfate-containing detergent composition which is anhydrous and substantially free of inert diluents.